Maul. Vader would have a powerful punch with all that armor, but if Vader cant hit Maul because hes too slow then Maul wins. And he is the fastest and strongest. Dooku wouldn't stand a chance. He is too old, and fat. And Palps... well his finger nails do work as claws, but still. Darth Maul would win.

Maul, if it's a quick fight. If it takes more than a couple of blows then I'm sure that Palpatine would be able to cheat himself to some kind of victory. Both Dooku and Vader are too honest to cheat or actually make use of their advantages.